Estrogen Endangers Fish Populations

Scientist Karen Kidd added synthetic estrogen to an artificial lake in Ontario, Canada, for three summers to track its impact on wildlife.

The pollution killed many fish and disrupted reproduction in others. The sperm count of male minnows fell, with some even beginning to produce eggs in their testes.

“We’ve known for some time that estrogen can adversely affect the reproductive health of fish, but ours was the first study to show the long-term impact,” Kidd said. “What we demonstrated is that estrogen can wipe out entire populations of small fish.”

The presence of hormonal pollutants in the country’s waterways is not new. According to Environmental Science and Technology magazine, scientists have been studying the impact of these chemicals on wildlife since the 1990s.

Intersex fish have been found in the St. Lawrence River, the Mississippi and the Great Lakes, Science Daily reports.

Wastewater, the source of the pollution, contains hormones because women excrete traces of estrogen, and many birth control drugs and household products contain compounds that chemically resemble hormones—called “hormone mimics.”

Still undetermined is what effect, if any, exposure to environmental hormones has on human health.

Scientists are studying whether hormonal pollutants “interact with the same receptor molecules inside the body that estrogen can,” Scientific American writes. If they do, the pollutants “might subtly overdose living things with excesses of hormone-like signals.”

Thankfully, the magazine reports that a number of studies into whether the pollutants contribute to breast cancer and other human health issues have provided insufficient “evidence, at least at the present, for such effects of exposure to an environmental estrogen.”

After a seven-year research effort, Canadian biologists found that miniscule amounts of estrogen present in municipal wastewater can decimate wild fish populations living downstream. Kidd’s study, first published in 2007, was presented at the 2008 American Association for the Advancement of Science (AAAS) conference during a session entitled, "From Kitchen Sinks to Ocean Basins: Emerging Chemical Contaminants and Human Health."

The Economist summarizes Dr. Kidd’s findings and says, “There is a strong suspicion that if this oestrogen is not removed during sewage treatment (some works do, some do not), it causes serious damage to rivers and lakes."

In May 2007, Dr. Kidd explained to National Geographic that even a small amount of estrogen can impact fish. "It doesn't take a lot of estrogen to feminize male fish and, based on the results of our experiment, to impact fish populations,” she told the magazine.

The U.S. Geological Survey has published a report finding a high incidence of intersex fish in the Potomac River. Vicki Blazer, a USGS scientist, explained, "The fish from the sites with the highest human population density and the most farming had the highest incidences of intersex. On the Shenandoah, rates of intersex were highest, ranging from 80–100 percent intersex."

The Encyclopedia of Science and Technology Online reviews the various sources of hormonal pollutants. “There are many chemicals in our environment that can mimic the natural estrogen that animals make to regulate their sexual development and reproductive systems. These include detergent additives, synthetic estrogens found in birth control pills and estrogen replacement therapy drugs, plastics additives, some pesticides, and livestock hormones.” Many of these end up in our wastewater and sewage.

A Scientific American article asks whether there is “any conclusive research linking estrogen mimickers (such as organochlorines) to breast cancer or to other health effects?” The article provides a detailed review of recent studies on the potential effects on human health of chemical pollutants. It concludes, "The epidemiological data … when taken together do not provide evidence, at least at the present, for an effect of exposure to an environmental estrogen; the data are actually contradictory to the notion.”

An article by Penn State University Professor Ike Shipley argues that hormone pollution may already be affecting certain aspects of human health. Pointing to measures already taken by some European countries to control pollution and limit the use of hormonal chemicals, Shipley argues that regulators should err on the side of caution and impose tighter controls.

Steven Bay, a toxicologist with the Southern California Coastal Water Research Project in Costa Mesa, told the Los Angeles Times, “Sewage-treatment plants only remove 50 percent to 70 percent of these chemicals." This means the remaining 30 to 50 percent of chemicals, including estrogen, may eventually find their way into lakes and rivers.